Android中的R库错误

Question

I have been using this Android Guide

While it has been a pleasant experience so far, I am experiencing my first problem. I copied all the code from the source that is in the link, and pasted it to the project folder, replacing all old files.

Before starting to understand what I had pasted, I thought it would be logical to run the code first to check for problems. The project wouldn't run because of an R object missing. After importing it (Eclipse's solution to the problem), more errors popped up. I tried searching for an answer, both on the Internet and in the book, but to no avail.

Since my software is up to date, I doubt this is a problem on the software's side. And since the code is available online, I think the problem would have popped up and been fixed.

Thank you in advance for the help. For extra details please ask in the comments.

The code:

    MainActivity.java

        package com.dummies.android.silentmodetoggle;

        import android.app.Activity;
        import android.graphics.drawable.Drawable;
        import android.media.AudioManager;
        import android.os.Bundle;
        import android.util.Log;
        import android.view.View;
        import android.widget.Button;
        import android.widget.ImageView;

        public class MainActivity extends Activity {

        private AudioManager mAudioManager; 
        private boolean mPhoneIsSilent;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

            mAudioManager = (AudioManager)getSystemService(AUDIO_SERVICE);

            checkIfPhoneIsSilent(); 

            setButtonClickListener();

            Log.d("SilentModeApp", "This is a test");
        }    

        private void setButtonClickListener() {
         Button toggleButton = (Button)findViewById(R.id.toggleButton); 
         toggleButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                if (mPhoneIsSilent) {
                    // Change back to normal mode
                    mAudioManager
                            .setRingerMode(AudioManager.RINGER_MODE_NORMAL);
                    mPhoneIsSilent = false;
                } else {
                    // Change to silent mode
                    mAudioManager.setRingerMode(AudioManager.RINGER_MODE_SILENT);
                    mPhoneIsSilent = true;
                }

                // Now toggle the UI again
                toggleUi();
            }
        }); 
       }

    /**
     * Checks to see if the phone is currently in silent mode. 
     */
    private void checkIfPhoneIsSilent() {
        int ringerMode = mAudioManager.getRingerMode();
        if (ringerMode == AudioManager.RINGER_MODE_SILENT) {
            mPhoneIsSilent = true;
        } else {
            mPhoneIsSilent = false;
        }

    }

    /**
     * Toggles the UI images from silent
     * to normal and vice versa.
     */
    private void toggleUi() {

        ImageView imageView = 
            (ImageView) findViewById(R.id.phone_icon);
        Drawable newPhoneImage;

        if (mPhoneIsSilent) {
            newPhoneImage = 
                getResources().getDrawable(R.drawable.phone_silent);

        } else {
            newPhoneImage = 
                getResources().getDrawable(R.drawable.phone_on);
        }

        imageView.setImageDrawable(newPhoneImage);
    }

    @Override
    protected void onResume() {
        super.onResume();
        checkIfPhoneIsSilent();
        toggleUi();
    };
}

Answer 1

Try cleaning your project, this will rebuild your R file. If there is still no R file in your file-tree then you may have an error in one your xml layout files. Eclipse may not tell you this so be vigilant and check through all the files in the /res folder.

Also, never import R when this happens.

Answer 2

您是否检查/res/values/string.xml中是否存在名为action_settings的变量（如果不存在），请创建一个变量，然后使用项目进行清理->清理自动生成的 makeure